1. Field of the Ivention
The present invention generally relates to the use of a controllable pitch propeller and, more particularly, to a means for manipulating the pitch setting of a controllable pitch propeller during gear shifting operations from neutral to an in-gear setting or from a first in-gear setting to a second in-gear setting.
2. Description of the Prior Art
Many different types of controllable pitch propellers are well known to those skilled in the art. U.S. Pat. No. 4,906,213, which issued to Esthimer on Mar. 6, 1990, describes an apparatus for detecting the pitch of a marine controllable pitch propeller. The pitch is detected by a motion/DC current transducer in the propeller hub. Circuitry rotating with the propeller shaft converts an AC power signal to DC for energization of the transducer and converts a DC output signal from the transducer to AC. The AC power and output signals are transferred from the rotating circuitry to a stationary circuit in the vessel hull by rotary transformers. There are no contacts between relatively moving parts of the transducer or rotary transformers, thus ensuring long life for the pitch detection system.
U.S. Pat. No. 4,900,280, which issued to Midttun on Feb. 13, 1990, describes an apparatus for detecting the pitch of a marine controllable pitch propeller. The pitch setting of a marine controllable pitch propeller is indicated with a high accuracy by comparing the positions of the portions within the vessel hull of a translating member fastened to the pitch change mechanism with the propeller hub and a non-translating member fastened adjacent one end to the hub and extending essentially free of axial load through the propeller shaft into the vessel hull.
U.S. Pat. No. 5,213,472, which issued to Dumais on May 25, 1993, describes an inboard servo for marine controllable pitch propellers. The inboard servo is of the force rod type and comprises a feedback device comprising a feedback ring located externally of the propeller driveshaft and affixed to the force rod for rotation and axial translation therewith. It also has a planar surface perpendicular to the propeller driveshaft axis and a distance-measuring device for substantially continuously detecting the position of the ring, and therefore the position of the force rod. The distance-measuring device directs a high frequency pulsed signal onto the ring surface from a fixed position spaced apart therefrom, detects the signal as it is reflected by the ring surface from a fixed position spaced apart therefrom, and processes the directed and reflected signals to produce a signal indicative of the position of the ring surface based on the time difference between the pulses directed onto the ring surface and the pulses reflected from the ring surface.
U.S. Pat. No. 4,028,004, which issued to Wind on Jun. 7, 1977, describes a feathering controllable pitch propeller. The propeller has blades carried by a hub and a hydraulic actuator housed in the hub and coupled to the blades for altering the pitch angle of the blades in both directions, astern and ahead, and also beyond the ahead to a feathered position. A servo-control system controls the actuator to adjust the blade pitch angle, the control system having a blade position feedback loop by which the system operates with positional feedback over the range of pitch angle between astern and full ahead pitch angles. However, the demand signal for blade feathering renders the feedback loop inoperative, and the hydraulic actuator then moves the blades into the feathering position without feedback action.
U.S. Pat. No. 3,249,161, which issued to Schoenherr on May 3, 1966, describes a feathering controllably pitch propeller. The invention relates to marine propellers and more particularly to a propeller which will reduce the fluctuations of the propeller forces and thus minimize vibrations.
U.S. Pat. No. 2,812,026, which issued to Braddon on Nov. 5, 1957, describes a variable pitch propeller control system. The invention relates to systems for controlling the pitch of the blades of variable pitch propellers and, particularly, to improvements in power actuating and regulating devices for such systems as applied in the field of marine propulsion.
One characteristic that is incumbent in most marine propulsion systems is that a shock load is typically experienced by the propulsion system when the transmission is moved from neutral to either forward or reverse gear or, alternatively, if the transmission is moved from forward to reverse or from reverse to forward. One cause of this shock load, which produces an audible sound, is that the xe2x80x9cdog clutchxe2x80x9d or xe2x80x9ccone clutchxe2x80x9d of the marine propulsion system provides no mechanical damping during the shifting operation. Since the clutch is used to connect, in torque transmitting relation, a torque transmitting shaft with a stationary propeller hub, the initial resistance to movement exhibited by the propeller hub creates the impact sound. The propeller hub has inertia because of its mass and shape. In addition, the blades of the propeller experience resistance to rotation about the propeller shaft axis because this rotation is resisted by the presence of water that must be moved by the propeller blades in order for rotation of the propeller to be possible.
In would therefore be significantly beneficial if a method could be provided to reduce the shock load on the marine propulsion system when the transmission is shifted into an in-gear setting from either the neutral gear setting or another in-gear setting.
A method for operating a controllable pitch propeller of a marine propulsion system, according to a preferred embodiment of the present invention, comprises the steps of monitoring a gear condition status, recognizing a future occurrence of a change in gear condition status, and determining a current pitch setting of the controllable pitch propeller. The method of the present invention further comprises of causing the controllable pitch propeller to change from the current pitch setting to a gear shifting pitch setting before the gear condition status changes and changing the controllable pitch propeller from the gear shifting pitch setting to a subsequent pitch setting after the gear condition status changes.
The gear shifting pitch setting, in a preferred embodiment of the present invention, is a lower pitch setting than the current pitch setting. The subsequent pitch setting is generally equal to the current pitch setting. The gear shifting pitch setting can be generally equal to a zero pitch setting.
The future occurrence of a change in gear condition status can be either a change from a neutral position to a forward position, or a change from one in-gear position to another in-gear position.
The monitoring step of the present invention can comprise a step of receiving a signal from a gear selector switch. The monitoring and recognizing steps can be performed by a microprocessor and the microprocessor can be a part of a propulsion control module (PCM).